The present invention relates to a safety coupling having a first drive/output element that, via a coupling mechanism which is disengaged against spring force at a predetermined maximum torque, is connected to a coaxially disposed second drive/output element.
Safety couplings of this general type are known. Their task is to protect machines from becoming overloaded by limiting the torque that can be transmitted, and to prevent damage to tools and workpieces. Such couplings are generally installed on shafts at that location where the greatest torque occurs during sudden retardation of the load.
In one known safety coupling of the aforementioned general type, which is designated as a "free shifting coupling", the two drive/output elements are connected via a coupling mechanism that is provided with a row of ball bearings that are disposed along the periphery of a ball race that is connected with one of the drive/output elements. The ball bearings are under the effect of a pressure disk upon which acts the force of a cup or plate spring; due to the force of this plate spring, the ball bearings are partially pressed out of the ball race and into cups disposed on a flange ring that is connected to the other drive/output element. When a prescribed maximum torque is exceeded, which torque is determined by the force of the plate spring, the ball bearings are pressed out of their cups and are displaced against the force of the plate spring. In this state, the coupling is disengaged and remains in this state under the effect of an arresting mechanism. A drawback of this known free shifting coupling is that even when the coupling is disengaged, a frictional moment is transmitted as a result of the ball bearings that are disposed between the flange ring and the pressure plate, with considerable material wear occurring at this location. This is a tremendous drawback, especially if the safety coupling is to be used on machines that still have a long slow-down time after the coupling has been disengaged and the machine has been turned off.
It is therefore an object of the present invention to provide a safety coupling of the aforementioned general type that operates as a free shifting coupling and that in the disengaged state exhibits only minimal frictional moment, so that in particular the coupling mechanism itself is no longer subjected to any frictional forces that produce wear.